Adjustable finishing end for broaches



Aug'. 13, 1929. F. J. LAFQINTE Y f 1,724,669

V ADJUSTABLE FINISHING END FOR BROACHES FiledAug. 16, 192'? I Patented ugf 13, 1.929.

UNITED STATES FRANCIS J. LAPOINTE, 0F .ANN ARBOR, MICHIGAN.

ADJUSTABLE FINISHING END FOR BROACHIE'S.` I

Application filed August 16, 1927. SerialNo. 213,312.

This invention relates to broaches and has for its object the provision of a finishing end for said broaches which may be adjusted so that its cutting edges will extend beyond the peripheries of the main broach` cutters and cause the hole being broached to have the exact diameter required. o

This object is attained by the device illustrated in the accompanying drawings.

For the purpose of illustrating the invention, one preferred form thereof is illustrated in the drawings, this form having been found to give satisfactory and reliable results, although it is to be understood that the variousv instrumentalities of which the invention consists can be variously arranged and organized, and the invention is not lim-y ited to the precise arrangement and organization Vof these instrumentalities as hereink shown and described except as required by the scope of the appended claims. v

Of the drawings:

Figure 1 represents a side elevation of a portion of a broach showing in section thereon an adjustable and expandable finishing member embodying the principles of the present invention.

Figure 2 represents' a side elevation of the same in connection with a hole in material being broached and the finishing member slightly expanded.

Figure 3 represents an end elevation of the same. p

Figurefi represents an elevation of the outer end of the expandable finishing member, and

Figure 5 represents an elevation of the inner end thereof.

Similar characters indicate 'like parts throughout the several figures of the drawmgs provided with a plurality of annular cutters 11, 11x which are separated from each In the drawings 10 is a portion of a broach After the last cutter 11 passed through the work 1t is necessary to finish and smooth the hole being broached and this is usually accomplished by a plurality of additional .of cutting a hole very accurately, in many cases the demand being that the hole mustnot'vary more than one ten thousandths of aninch.

Now if a hole is required to be finished to a size ofsay 1.2501 inches, the manufacturer of the broach must judge by previous experience just how many ten thousandths of an inch larger the broach must be made to compensate for the s ring of the metal and still make the hole o the required size.

All sorts of material are operated upon, that is, bar stock, forgings, castings, etc., none of which are of the same degree of hardness, and conse uently the broach will cut freer in one lot o material than in other lots of material.

The result is that in many cases the piece of material being breached will not pass rinspection and this is a consequent loss both in labor and material. v

It is obvious, therefore, that it is most desirable to provide each broach with some means-on its finishing end which may be expanded so that it-may be set to within one ten thousandthsof an inch of the size of the hole required.

This requirement is fully met bythe construction of broach herein shown and described.

In my improved broach the finishing end A thereof is provided with an axially disposed tapered extension 14, the wall of which has an inclination of substantially one half inch per foot. v A

From the outer end of this tapered extension 14: projects the threaded shank 15 onvr which is mounted a nut 16.

Surrounding the tapered extension 14 is an adjustable finishin shell 17 consisting of a helically wound strip of material 17x the winds of which are normally in contact as shown in the drawin Under normal cond1tions the inner end of the shell 17 is spaced from thepshoulder 18 at the end of the body of the broach.

doing the shell is expanded to increase thediameter of the helically wound tooth 19.

By this means it is-quite an easy matter to make sufficient adjustment to allow for any differences in metal or in slight wear of the preceding sizing cutters 11", it beingunderstood that on`the finishing end of the body of the broach 10, there are usually a plurality of cutters 11x which are left full size.

When the shell- 17 is placed upon the tapered extension 14 the diameter of the 'helically disposed cutting tooth 19 is also full size or the same diameter as that of the sizing cutters 11". i

If the operator discovers that the broached hole is `one or two ten thousandths of an inch too small in diameter, all that he needsI to do is to turn the nut 16 slightly thereby expanding the lshell 17, broach a piece of material land calibrate it, repeating the operation until the shell 17 is expanded sufficiently to broach the size of hole required.

By Vmeans of this broach With its adjustable shell 17 not only may the differences in the material being broached be taken care of but it also provides means whereby-the variation in size of the broach due to wear may be compensated for.

This is of greatl importance as by providing the broach with the adjustable and expandable shell 17 the purchaser of the broach isable to obtain anywhere from eight to ten times the life out of the tool than could be obtained from a solid broach performing the same operations.

It has been found by actual practice that the shell 17 may be expanded as much as .O12 of an inch which is twice the expansion ever required when the broach is in actual use.

It is believed that the operation yand many advantages of the invention will be understood readily without further description.

Having thus described my invention, I claim:

1. A broach provided with a reduced tapered end with an unbroken peripheral surface; a helical member fitted to said tapered end and havingan outwardly eX- tending undercut cutting tooth following each wind thereof, Said member being shorter than said tapered end; and means adjustable onl said broach for forcing said member endwise on said tapered end and expanding it for its entirelength.

2. A broach provided with a reduced tapered end with an unbroken peripheral surface; a helical member fitted to said tapered end yand having an outwardly extending undercutl cutting tooth following'` each wind thereof, said member being shorter than said tapered end; and means adjustable on said broach for forcing said member endwise on said tapered end and increasing the diameter of the cutting tooth throughout the entire length of said member.

3. A broach having a plurality of peripheral cutters and provided with a reduced tapered end with an unbroken peripheral surface; a member fitted to said tapered end and consisting of a helically wound strip with a continuous tooth following the winds thereof, said member being shorter than said tapered end with one end extending beyond the extremity of said tapered end; and adjustable means coacting with said outer end for forcing said member endwise and expanding said member from end to end with the periphery of said tooth beyond the peripheries of said cutters.

4. A broach having a plurality of peripheral cutters integral therewith and provided with a tapered end with an unbroken peripheral surface; a removable helically wound member fitted to and movable endwise of said tapered end,.one end of said member extending beyond the extremity of said tapered end and said member-having a continuous cutting tooth followin the winds thereof; and means coacting with the outer end of said helically wound member for forcing it toward the larger end of said tapered `end and expanding said member equally from end to end.

5. A broach having a plurality of peripheral cutters integral therewith and provided with a tapered end with an unbroken peripheral surface and a threaded shank extending therefrom; a removable helically wound member fitted to and movable endwise of said tapered end and having a continuous tooth following the winds thereof; and a nut on said shank coacting with one end of said member for forcing it endwise of the tapered end and expanding said member equally from end to end and increase the diameter of the periphery of said tooth.

Signed by me at Ann Arbor, Michigan, this 10th day of August, 1927.

FRANCIS J. LAPOINTE. 

